Collins’ victory was based on an analysis of voter interviews, conducted for The Associated Press by Edison Media Research and Mitofsky International.

Collins’ message of bipartisanship and independence trumped the sixth-term congressman’s attempt to link her to President Bush’s policies on Iraq, the economy, health care and energy.

Both candidates raised roughly $13 million between them in the most expensive campaign in Maine history, exceeding the previous mark by $5 million.

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Also up for grabs were two congressional seats, including the one that Allen vacated when he sought to move up to the Senate.

In the 1st Congressional District, Democrat Chellie Pingree was favored over Republican Charlie Summers, who ran unsuccessfully against Allen in 2004.

To the north, in the 2nd District, Democratic incumbent Michael Michaud was seen as a shoo-in over Republican newcomer and self-proclaimed contrarian John Frary.

Ticket-splitters broke for Collins, who had been leading in the polls by double digits throughout the campaign, while giving Democrat Obama an overwhelming victory over Republican John McCain in a state that has been carried by the Democratic nominee in the last four presidential elections.

During the Senate campaign, Collins promoted her credentials as a pragmatic and independent-minded centrist whose ability to draw bipartisan support has made her an effective legislator.

Allen sought to tie her to President Bush, asserting that she has been on the wrong side on major issues, but his campaign never seemed to gain traction.

The unprecedented campaign spending bankrolled a flood of television ads, which have been supplemented by spots financed by third-party groups.

The race was viewed as a test of whether moderate Republicans have a future in the Northeast, where Collins and fellow Maine Sen. Olympia Snowe are among the last survivors of the breed. Democrats were buoyed by the defeat two years ago of Rhode Island Sen. Lincoln Chafee, which demonstrated that even a personally popular Republican is at risk in New England, and hoped for a similar outcome in Maine.

Pingree, a former legislator who ran against Collins six years ago and then went on to head the advocacy group Common Cause, outspent Summers by roughly 4-1. Summers got a late start in the campaign, having been on active duty with the Navy in Iraq during much of the primary season while his wife filled in for him during campaign events.

Michaud, a former paper mill worker and state Senate president, served three terms in Congress, where he aligned himself with the conservative Blue Dog Democrats. Frary, a retired college professor, came across as a modern-day W.C Fields while making a point of not taking his campaign too seriously.